Alliums (gouache style)

Ornamental alliums are relatives of the onion, grown for their ball-shaped heads of small starry flowers held on bare stems. 'Purple Sensation' is an early, reliable variety; 'Globemaster' makes huge lilac heads, and Allium cristophii has loose, metallic-looking spheres that dry beautifully. The drumstick allium, Allium sphaerocephalon, flowers later with small egg-shaped heads. Their strap-shaped leaves often yellow by the time the flowers open, which is normal.

Plant bulbs from September to November in full sun and well-drained soil, at about three times their own depth. Because the leaves fade as the flowers open, they're best grown among perennials or grasses that hide the untidy foliage. They need little feeding. Bees visit them heavily in May and June. Once the colour has gone, don't cut the stems: the seed heads stand well into autumn and winter. Congested clumps can be lifted and divided in autumn.

Purple allium globes float on tall stems among grasses and ferns in this image. The setting shows exactly how they're best grown, rising above softer foliage that covers their own fading leaves. The moment chosen is full bloom, when the spheres are at their roundest and richest purple.